1. Field of the Invention
The present invention relates to a blood purification device which purifies blood from a patient in extracorporeal blood circulation.
2. Discussion of the Related Art
In dialysis treatment, a blood circuit consisting mainly of flexible tubing is used to place the blood of a patient in extracorporeal blood circulation. This blood circuit arrangement includes an arterial blood circuit having an arterial needle at one end to collect blood from the patient and a venous blood circuit having venous needle at one end to return the blood to the patient. A dialyzer can be incorporated between the arterial blood circuit and the venous blood circuit.
A roller blood pump is placed in the arterial blood circuit. By driving the pump, the blood of the patient is collected through the arterial needle and flows extracorporeally through the arterial blood circuit, the dialyzer, and the venous blood circuit. There are multiple hollow fibers inside the dialyzer. The blood flows through each hollow fiber.
Projections are formed on the dialyzer case, one being a dialysate inlet port and the other being a dialysate outlet port. Dialysate of predetermined concentration is supplied in through the dialysate inlet port, along the outside of the hollow fiber (i.e., between the outside surface of the hollow fibers and inside surface of the dialyzer case), and then out through the dialysate outlet port.
The walls of hollow fibers, which contain micropores, form blood purifying membranes. Waste products of the blood passing through the inside of the hollow fibers are dialyzed to the dialysate through the blood purifying membrane and the purified blood returns to the patient. To remove water from the blood of the patient during the dialysis treatment, the dialysis device includes a ultrafiltration pump.
Japanese laid open patent publication number H09-149935 disclosed a monitoring means for the amount of water to be removed which comprises a comparison between the real-time blood concentration measured and the blood concentration calculated from a blood flow rate of the blood pump and a water removal rate. The blood concentration (hematocrit value) measured from the passing blood through the dialyzer with one pair of a light emission means and a light reception means in the venous blood circuit.
As disclosed in the Japanese laid open patent publication number H0-149935, the blood purification device which measures the blood concentration from the passing blood through the dialyzer with the light sensor; monitors the amount of water to be removed by comparing between the real-time blood concentration measured while dialyzing and the theoretical value of the blood concentration calculated from the blood concentration measured prior to dialysis, a blood flow rate in the blood pump and a water removal rate. Accordingly, the errors regarding the amount of water removal are reduced, and consequently, the worsening of the patient's condition due to water removal error can be prevented.